1. Field of the Invention
The present invention relates to a lens frame shape measuring apparatus for measuring the shape of a lens frame of glasses.
2. Description of the Prior Art
Conventionally there has been invented a lens frame shape measuring apparatus in which a contact element is brought into abutment against a groove formed in a lens frame of glasses to measure the shape of the lens frame.
According to a conventional lens frame shape measuring apparatus of this type, a lower end of a U-shaped arm is integral with an upper end of a vertically extending rotary shaft, a contact element is provided at an upper end of the arm, the contact element and the rotary shaft are urged together toward a lens frame groove by means of a spring, thereby allowing the contact element to abut the lens frame groove at a predetermined pressure, and at the same time the rotary shaft is rotated in the same direction at a predetermined certain speed, thereby allowing the contact element to rotate along the lens frame groove.
There are certain lens frames which are narrow in rim width in a direction perpendicular to an optical axis of a lens of glasses and are therefore easily deformed under the action of an external force. There is a known lens frame for half glasses (called xe2x80x9cKanime lensesxe2x80x9d in Japanese) whose vertical width is extremely narrow when seen from the front side for example. A certain lens frame for half glasses is narrow in rim width and is easily deformed as noted above.
Therefore, when the shape of a lens frame for half glasses narrow in rim width and apt to be deformed is measured by the foregoing lens frame shape measuring apparatus, a nose contacting side or an ear contacting side of the lens frame for half glasses will be deformed if the rotating speed and direction of the contact piece are approximately constant as noted above, thus giving rise to the problem that an exact shape of the lens frame for half lenses cannot be measured.
In this measurement, the deformation of the lens frame for half lenses is conspicuous particularly on the ear contacting side and it is a largely protruding deformation to the outside in comparison with a normal shape, thus making it impossible to obtain exact data on the lens frame shape.
Therefore, when it is taken into account that the measurement must also cover measuring the shape of such a lens frame for half glasses which is narrow in rim width and is apt to undergo deformation, it is difficult to realize a complete automation of the lens frame shape measurement with use of the lens frame shape measuring apparatus.
Accordingly, it is the first object of the present invention to provide a lens frame shape measuring apparatus wherein the shape of a lens frame of glasses is identified on the basis of the distance from a movement start position of a contact element at a lens frame center up to a lens frame measurement start position at which the contact element is first brought into abutment against the lens frame, i.e., a vertical moving distance of the contact element as seen from the front side of the lens frame in the measurement, and can be used in judging whether contact measurement conditions such as rotating speed and direction of the contact element should be changed or not (a lens frame shape measuring sequence is to be changed or not), and which can realize a complete automation of lens frame measurement without human assistance.
According to the present invention, for achieving the above-mentioned object, there is provided a lens frame shape measuring apparatus wherein a contact element supported by a contact element moving mechanism is brought into abutment against a groove formed in an inner peripheral surface of a lens frame of glasses and is moved along the said groove to measure the shape of the lens frame by a moving position of the contact element, the apparatus comprising a contact element moving distance detecting means for detecting a moving distance of the contact element when the contact element is moved from a movement start position at the center of the lens frame up to a central position in the right and left direction of a lower rim of the lens frame and is brought into contact with the lower rim, and a measurement control means which identifies a lens frame shape of the glasses by the moving distance detected by the contact element moving distance detecting means and which controls a contact measurement state of the contact element for the lens frame in accordance with a measurement sequence corresponding to the thus-identified lens frame shape.
The contact element moving mechanism may comprise a slide base capable of moving forward and backward horizontally, a measuring section moving motor for moving the slide base forward and backward horizontally, a rotary base held by the slide base horizontally rotatably, a base rotating motor for rotating the rotary base, an upper slider mounted to the rotary base so as to be movable forward and backward horizontally and holding the contact element vertically movably, and a spring which urges the upper slider in either the forward direction or the backward direction, and the measurement control means may control the operation of the base rotating motor and thereby control the state of movement of the contact element for the lens frame as the foregoing contact measurement state in accordance with the measurement sequence corresponding to the identified lens frame shape.
It is the second object of the present invention to provide a lens frame shape measuring apparatus wherein the rotating speed and direction of a contact element can be changed at a portion of a lens frame shape of glasses at which portion the radius of curvature varies largely and a contact pressure between the contact element and the lens frame is large.
For achieving this object, the contact element moving mechanism comprises a slide base capable of moving forward and backward horizontally, a measuring section moving motor for moving the slide base forward and backward horizontally, a rotary base held by the slide base horizontally rotatably, a base rotating motor for rotating the rotary base, a lower slider mounted to the rotary base horizontally movably, a drive motor for moving the lower slider forward and backward horizontally, an upper slider mounted to the rotary base so as to be movable forward and backward horizontally and holding the contact element vertically movably, and a spring which urges the upper slider in either the forward direction or the backward direction, and the measurement control means may control the operation of the drive motor and thereby control a contact pressure of the contact element against the lens frame as the foregoing contact measurement state in accordance with the measurement sequence corresponding to the identified lens frame shape.
The contact element moving mechanism may comprise a slide base capable of moving forward and backward horizontally, a measuring section moving motor for moving the slide base forward and backward horizontally, a rotary base held by the slide base horizontally rotatably, a base rotating motor for rotating the rotary base, a lower slider mounted to the rotary base horizontally movably, a drive motor for moving the lower slider forward and backward horizontally, an upper slider mounted to the rotary base so as to be movable forward and backward horizontally and holding the contact element vertically movably, and a spring which urges the upper slider in either the forward direction or the backward direction, and the measurement control means may control the operation of the base rotating motor and thereby control the state of movement of the contact element for the lens frame as the foregoing contact measurement state in accordance with the measurement sequence corresponding to the identified lens frame shape, and at the same time the measurement control means may control the operation of the drive motor and thereby may control a contact pressure of the contact element for the lens frame as the foregoing contact measurement state in accordance with the measurement sequence corresponding to the identified lens frame shape.
Further, the measurement control means may identify the lens frame to be a lens frame for half glasses when the moving distance detected by the contact element moving distance detecting means is smaller than a preset value.
Further, the measurement control means may be constructed such that when it judges that the lens frame is a lens frame for half glasses, it controls to decrease the rotating speed of the contact element relative to the rotating speed thereof for normal lens frame measurement, thereby creating a contact measurement state in which the contact element does not exert an abrupt deforming force on the lens frame when the measuring element moves along and in contact with the lens frame.
Further, the measurement control means may be constructed such that when it judges the lens frame to be a lens frame for half glasses, it controls to decrease the rotating speed of the contact element at a position on a nose or ear contacting side of the lens frame of glasses, thereby creating a contact measurement state in which an abrupt deforming force is not exerted on the lens frame when the contact element moves in contact with the lens frame at a position on the nose or ear contacting side of the lens frame of glasses.
It is the third object of the present invention to provide a lens frame shape measuring apparatus wherein, in the case of a lens frame for half glasses having an extremely narrow width in the vertical direction as seen from the front side of the lens frame for example and having a narrow rim width in a direction perpendicular to an optical axis of a lens of the glasses fitted in the lens frame, the shape of the lens frame can be measured accurately without deformation of the lens frame on a nose or ear contacting side.
For achieving this object, the measurement control means may be constructed such that when it judges that the lens frame is a lens frame for half glasses and that right and left portions of a lower rim of the lens frame are curved largely, while right and left portions of an upper rim of the lens frame are curved to a small extent, it controls to let the contact element move in contact with the lens frame while allowing the contact element to rotate from the lower rim toward the upper rim on the nose contacting side, thereby creating a contact measurement state in which the upper rim does not undergo an abrupt deforming force from the contact element on the ear contacting side.
Further, the measurement control means may be constructed such that the operation of each of the motors is controlled, allowing the contact element to measure both an outer peripheral surface of the lens frame and the lens frame groove, allowing the position of the outer peripheral surface of the lens frame and the position of the lens frame groove to be determined in accordance with measurement signals provided from the contact element moving distance detecting means, a difference between the position of the outer peripheral surface of the lens frame and the position of the lens frame groove is determined as a rim width, and if the rim width thus determined is smaller than a predetermined value and hence the lens frame is apt to be deformed, the operation of the drive motor is controlled to diminish the contact pressure of the contact element against the lens frame which contact is ensured by the spring.
Further, the contact element moving mechanism may comprise a slide base capable of moving forward and backward horizontally, a measuring section moving motor for moving the slide base forward and backward horizontally, a rotary base held by the slide base horizontally rotatably, a base rotating motor for rotating the rotary base, an upper slider mounted to the rotary base so as to be movable forward and backward horizontally and holding the contact element vertically movably, a spring which urges the upper slider in either the forward direction or the backward direction, and a manual measurement force changing means which changes over the upper slider urging force of the spring to change over the contact pressure of the contact element against the lens frame.